Mīmāmsa Sūtra 01.01.22

प्रख्याभावाच्च योगस्य ॥१-१-२२॥

prakhyābhāvācca yogasya ॥1-1-22॥

[प्रख्या (prakhyā) - manifestation; अभावात् (abhāvāt) - from absence; च (ca) - and; योगस्य (yogasya) - of union;]

And because of the absence of manifestation, there is no union.

(Though sound may appear to manifest from air, when we speak, it is different from air as it has no sense of touch and thus is not manifested and is not born out of union with the air. Thus, it is eternal.)